For tunneling diode devices, the separation of the electrodes is necessarily very small (<1–10 nm) so that electrons may tunnel from an emitter electrode to a collector electrode. Performance of such a device is very dependent on creating and maintaining a gap having such small dimensions.
In U.S. Pat. No. 6,417,060 Tavkhelidze et al. disclose a method for manufacturing a pair of electrodes in which topological features in one electrode are matched in the other. The method involves fabricating a first electrode with a substantially flat surface and placing a sacrificial layer over it. A further material is placed over the sacrificial layer. The sacrificial layer is removed with an etchant. Alternatively, the sacrificial layer is removed by cooling the sandwich with liquid nitrogen, or alternatively still, the sacrificial layer is removed by heating the sacrificial layer, thereby evaporating the sacrificial layer. Electrodes so formed may be placed in close proximity, 5 nm or less.
Using such a pair of electrodes in a tunneling diode device may be limited by nanoscale roughness; peaks, ridges, etc in one electrode that have dimensions sufficiently great that they contact the other electrode and prevent flatter regions from coming into sufficiently close proximity to allow tunneling.
There remains a need therefore for reducing nanoscale roughness on electrode surfaces.